In a typical digital radio communication system, information throughput tends to be limited by channel bandwidth, and channel modulation and information encoding techniques. Channel modulation and bandwidth are ordinarily fixed for a particular communication channel, and are determined based on external constraints imposed on the system, or overall system design. Digital information is frequently encoded to support error mitigation. Accordingly, encoding requirements may vary depending on the type of data being transmitted. For example, a given desired error mitigation level may require a particular data encoding rate. The encoding rate and encoding technique used affect the overall information throughput.
One commonly used encoding technique is that of convolutional encoding. FIG. 1 is a flowchart of procedures 100 summarizing the encoding process. Here, data symbols are obtained for transmission, step 110, and mapped to output data symbols using a finite encoder state machine that implements a specific encoding format, step 120. The output symbols are then modulated on a carrier signal, step 130, and the modulated signal transmitted on a communication channel, step 140.
At a receiving end, a Viterbi algorithm, or a derivation thereof, is a popular way of decoding convolutionally encoded information. The Viterbi algorithm is an efficient way of determining the likelihood that a particular received symbol represents a transmitted symbol that may have been influenced by noise in the transmission channel. The Viterbi algorithm uses the fact that a convolutional encoder is a state machine in which each input symbol causes a state transition and an associated output symbol. Thus, in a prior art applications, the Viterbi algorithm depends on prior knowledge as to encoding state machine, i.e., there is prior knowledge of a specific decoding format.
Channel bandwidth, modulation technique, and error mitigation requirements impose constraints on the rate of transfer of digital symbols on a particular communication channel. However, it is desirable to increase throughput within these constraints. Therefore, a new digital communication technique is needed.